This morning two small asteroids passed harmlessly by Earth at distances of just 174,000 and 292,000 miles. 2012 XP134, the more distant and measuring 42 feet across, whizzed by at 8 a.m. (CST) and 40-foot -wide 2012 XL134 two hours later. While some may take the sign of so many Earth-approaching asteroids as a bad omen, it’s all good news in my view.

NASA estimates there are a total of about 10 million near-Earth asteroids in the 10-meter (32 feet) range with an expected impact rate of one every 10 years. If you up the size to 30-meters (100 feet), there are 1.3 million objects with an impact rate of one every 200 years. Objects this size are still too small to gouge a crater and cause significant damage on the ground. Most would be expected to fragment in an airburst and possibly drop meteorites along their entry paths.

This chart shows how data from NASA’s Wide-field Infrared Survey Explorer, or WISE, has led to revisions in the estimated population of near-Earth asteroids (NEAs). The infrared-sensing telescope performed the most accurate survey to date of NEAs. Small objects found weekly number in the millions. Click photo to learn more about asteroid numbers. Credit: NASA

With numbers like these, it’s no surprise that Earth-shaving asteroids are discovered routinely. According to Donald Yeomans, manager of NASA’s Near-Earth Object Program Office, asteroid search programs find about 20 every week. In tomorrow’s blog, I’ll be reviewing his brand new book on the topic.

I’m glad all these good people are watching out for flying rocks. Not only does it mean we humans are becoming more knowledgeable about our surroundings, but knowing their orbits allows us to forecast when one of them might pose a danger in the future. This, we hope, will stir us to devise solutions to avoid a potential disaster. In 1990 there were only 134 Earth-approaching asteroids known; as of mid-2012 that number is somewhere around 9,000 and rising every week. Wouldn’t you rather know what’s coming than be in the dark?

Flyby images of the 3-mile long asteroid Toutatis taken by the Chinese Chang ‘e 2 spacecraft earlier this week. Its odd shape might be the result of two separate asteroid fragments that stuck together after a gentle collision. Click for larger version. Credit: SASTIND via Weibo / UMSF

Many of us got to experience first hand this week what happens when minute pieces of an asteroid strike Earth’s atmosphere – a beautiful meteor shower! Thurday night’s Geminids originate from dust and small pebbles released from the 3.1 mile long asteroid 3200 Phaethon. Two nights prior to the Geminid peak, the largest near-Earth asteroid 3179 Toutatis, also about 3 miles long, passed some 3.4 million miles from the planet.

64-frame movie showing Toutatis tumbling through space only 4.3 million miles from Earth on Dec. 12-13. Credit: NASA/Goldstone radar

While Phaethon’s too faint for most amateur telescopes, Toutatis remains bright as it slowly travels through the constellations Cetus and Aries this month. I watched this star-mimic amble through my telescope field of view Thursday night while trying to appreciate exactly what I was looking at. Fortunately the Chinese and NASA’s Goldstone radar provided some help.

A cropped version of picture sequence shows a clearer view of the asteroid’s surface. The bumps could be piles of boulders. Credit: Chinese National Space Agency

As the spacecraft flew by the bizarre-shaped Toutatis at the relative speed of 24,000 mph, it snapped a series of approach pictures. Higher resolution images will soon be released, but these are clear enough to see what appear to be boulder piles strewn about the surface as well as shallow craters. We live in wonderful times.

Related

Post navigation

23 Responses

Jim Harstad

Hi Bob;

I just wanted to point out that the radar animation shows the object being “top-lit” instead of “front-lit” by the radar. This was brought up a couple of weeks ago in refernce to still radar images of a different object (in the comments section) and you suggested it might be a possible effect of rotation, but that doesn’t seem to be the case with this object. Could the sun cause that “lighting” effect as a radio source or do you think there is yet something else causing it?

Hi Jim,
Glad you’re still enjoying. As for the “light” in radar images coming from the top, I’ve got a partial explanation for it and am seeking a better one at the moment. It’s definitely not the sun but has to do with the time delay in the radio waves hitting and asteroid and then returning. As soon as I get a clear answer, I’ll let you know.

Da Boss,
While Toutatis is invisible with the naked eye, you can see it in a 6-inch telescope at about magnitude 11. As for the two that passed this morning, they were much too small and faint to show up in even in a bigger amateur telescope.

Jean,
Many are seen ahead of time, but yes, it’s possible one could be poorly positioned for observation, say, coming from the direction of the sun and unobserved until too late. Keep in mind, we’ve discovered to date about 90% of the large, catastrophe-making asteroids. Asteroids of that size (1-2 km) strike Earth only once every 700,000 years.

Jean,
Tiny asteroids in the 1-meter (3 feet) range hit Earth about every two weeks. Most go unseen over the oceans, but if burn up over a populated area, they produce spectacular fireballs. The chances of a globally catastrophic impact is exceedingly small. Like I said, once every 700,000 years. No such event has occurred within human memory. 2012DA will cruise something like 21,000 miles away, completely missing Earth. Even if a small asteroid like 2012DA gets relatively close to the planet, Earth can’t pull it in because the object is moving too rapidly in its own orbit to be captured.

Hi Bob
Well I for one is so glad that there is so many people out there that is keeping an eye out for any new one’s, like in the space of 1-2 days 8 small one’s have been found, which is fantastic considering how much harder it is to see them, so we can sleep a bit easier knowing this, looking forward to tomorrow to find out a bit more on Don’s book it should make a good read.

As we discussed earlier, the folks that have been misled to believe that because the Mayan “long count calendar” has an end date of 12/21/12 means some sort of “end” to life on earth instead of the BEGINNING of a new “era” for humankind are starting to really pay attention to anything and everything negative, bad, evil and just plain no good that’s going on. You know that if you have one person posting about a catastrophic collision with a NEO, there are probably a million that didn’t post.

This may be about the only time you should (or can) be pleased that your website isn’t as popular as some of the NASA and other government funded observatories around the world! Or you would be doing nothing but answering concerned “Internet surfers” posts, agree?

This is the only time I tend to get more than normally upset with the various types of “media” that have done everything in their power to get as many human beings worried, paranoid, concerned, etc. over something that has been taken the wrong way and then sensationalized. What’s the point in doing that? Do they make more money because of it? Sometimes I believe today’s “journalists” have forgotten the original purpose of reporting news and I know I’m not alone in thinking that way.

I’ve never looked forward to having a certain “date” on the calendar just “come and go” in my life. Imagine all the massive gatherings that will be happening on the evening of 12/20/12 and finally dispersing after midnight 12/22/12? I wonder how many employees will be calling in “sick” next Friday. LOL! I’m sure it’s bound to be one weird day.

Sorry for taking this space for venting, I will try to make this the last posting from me about this non-event.